1. Field of the Invention
The invention relates to lens systems and, particularly, to a projection lens system.
2. Description of Related Art
To provide a sharp projection image and reduce the size of projectors, such as digital light processing (DLP) projectors, liquid crystal display (LCD) projectors, or liquid crystal on silicon (LCOS) projectors, projection lens systems with high resolution and a short overall length (the distance between the magnification-side surface of such a projection lens and a surface of a spatial light modulator (SLM), e.g., digital micro-mirror device (DMD), LCD panel, or LCOS panel, equipped in a projector facing the projection lens) are employed. Factors affecting both the resolution and the overall length of the projection lens, such as the number and position of lenses employed, the refraction power distribution of the employed lenses, and the shape of each of the employed lenses, complicate attempts to increase resolution and shortening the overall length of projection lens systems. For example, although reducing the number of lenses can shorten the overall length of the projection lens system, resolution will suffer. Conversely, increasing the number of lenses can improve the resolution, but predictably, overall length of the projection lens is increased.
Therefore, it is desirable to provide a projection lens system which can overcome the described limitations.